Search PubMed⌕ Search

Biomedical subjects

Y Zhou

Publications and source records attributed to Y Zhou.

At least 955 records · Page 53Linked to original sources
PubMed1989

Surface spines of human blood flukes (Schistosoma mansoni) contain bundles of actin filaments having identical polarity.

The spines of Schistosoma mansoni have crystalline structures that have been suggested to consist of actin filaments. In this ultrastructural study, binding of heavy meromyosin to the actin filament spines strongly supports this view. Moreover, we reveal that all the packed actin filaments in the spines have the same polarity pointing away from the apical plasma membrane toward the basal membrane of the surface syncytial epithelium of the parasites and that the spine filaments interact indirectly with both the apical and basal membranes.

Actin Cytoskeleton↗
PubMed1988

Topology of the Mr 27,000 liver gap junction protein. Cytoplasmic localization of amino- and carboxyl termini and a hydrophilic domain which is protease-hypersensitive.

Hydropathy analysis of the Mr 27,000 rat liver gap junction protein sequence deduced from a cDNA clone has suggested the presence of four transmembrane segments (Paul, D. L. (1986) J. Cell Biol. 103, 123-134). In the present report, several features of the molecular topology of the protein were investigated by microsequence analysis of peptides generated by treatment of isolated gap junctions with a variety of proteases. Under the experimental conditions used, the proteases had access only to the portion of the Mr 27,000 protein that was originally (in vivo) the cytoplasmic surface of the gap junction. Microsequencing of the peptides resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates that the amino terminus of the protein is disposed at or near the cytoplasmic surface of the gap junction, and that this surface also contains a protease-hypersensitive hydrophilic sequence between residues 109 and 123, presumably connecting the second and third transmembrane segments. Immunocytological localization of binding of monoclonal antipeptide antibodies demonstrates that the carboxyl terminus of the protein is also localized to the cytoplasmic surface of the gap junction. No protease sensitivity was found in the hydrophilic sequences thought to connect either the first and second transmembrane segments or the third and fourth segments, supporting the model's prediction that these sequences face the narrow intercellular gap which cannot be penetrated by proteases.

Amino Acid Sequence↗
PubMed1988

Human kidney cathepsins B and L. Characterization and potential role in degradation of glomerular basement membrane.

Cathepsins B and L were purified from human kidney. SDS/polyacrylamide-gel electrophoresis demonstrated that cathepsins B and L, Mr 27000-30000, consist of disulphide-linked dimers, subunit Mr values 22000-25000 and 5000-7000. The pH optimum for the hydrolysis of methylcoumarylamide (-NHMec) substrates (see below) is approx. 6.0 for each enzyme. Km and kcat. are 252 microM and 364s-1 and 2.2 microM and 25.8 s-1 for the hydrolysis of Z-Phe-Arg-NHMec (where Z- represents benzyloxycarbonyl-) by cathepsins B and L respectively, and 184 microM and 158 s-1 for the hydrolysis of Z-Arg-Arg-NHMec by cathepsin B. A 10 min preincubation of cathepsin B (40 degrees C) or cathepsin L (30 degrees C) with E-64 (2.5 microM) results in complete inhibition. Under identical conditions Z-Phe-Phe-CHN2 (0.56 microM) completely inhibits cathepsin L but has little effect on cathepsin B. Incubation of glomerular basement membrane (GBM) with purified human kidney cathepsin L resulted in dose-dependent (10-40 nM) GBM degradation. In contrast, little degradation of GBM (less than 4.0%) was observed with cathepsin B. The pH optimum for GBM degradation by cathepsin L was 3.5. Cathepsin L was significantly more active in degrading GBM than was pancreatic elastase, trypsin or bacterial collagenase. These data suggest that cathepsin L may participate in the lysosomal degradation of GBM associated with normal GBM turnover in vivo.

Basement Membrane↗
PubMed1987

Kinetic, structural, and spectroscopic identification of geminate states of myoglobin: a ligand binding site on the reaction pathway.

Elementary steps or geminate states in the reaction of gaseous ligands with transport proteins delineate the trajectory of the ligand and its rebinding to the heme. By use of kinetic studies of the 765-nm optical "conformation" band, three geminate states were identified for temperatures less than approximately 100 K. MbCO, which is accumulated by photolysis between 1.2 and approximately 10 K, was characterized by our previous optical and X-ray absorption studies [Chance, B., Fischetti, R., & Powers, L. (1983) Biochemistry 22, 3820-3829]. Between 10 and approximately 100 K, geminate states that are also identified that have recombination rates of approximately 10(3) s-1 and approximately 10(-5) s-1 (40 K). Thus, it is possible to maintain a steady-state nearly homogeneous population of the slowest recombining geminate state, Mb, by regulated continuous illumination (optical pumping). Both X-ray absorption and resonance Raman studies under similar conditions of optical pumping show that the heme structure around the iron in Mb is similar to that of MbCO. In both geminate states, the iron-proximal histidine distance remains unchanged (+/- 0.02 A) from that of MbCO while the iron to pyrrole nitrogen average distance has not fully relaxed to that of the deoxy state. In MbCO the CO remains close to iron but not bound, and the Fe...CO angle, which is bent in MbCO (127 +/- 4 degrees C), is decreased by approximately 15 degrees [Powers, L., Sessler, J. L., Woolery, G. L., & Chance, B. (1984) Biochemistry 23, 5519-5523]. The CO molecule in Mb, however, has moved approximately 0.7 A further from iron. Computer graphics modeling of the crystal structure of MbCO places the CO in a crevice in the heme pocket that is just large enough for the CO molecule end-on. Above approximately 100 K resonance Raman studies show that this structure relaxes to the deoxy state.

Binding Sites↗
PubMed1986

The orientation bias of LGN neurons shows topographic relation to area centralis in the cat retina.

The orientation sensitivity of LGN cells to flickering square-wave gratings was measured in urethane-anaesthetized paralyzed cats. The mean ratio of the amplitude of peak responses to optimally oriented gratings to that elicited by gratings of the least effective orientation was 3.0 +/- 0.3 (S.E.). 58% of the recorded neurons responded best to orientations within 30 degrees of the meridional line joining their receptive field center with the fixation points (area centralis), implying that they were more sensitive to visual contours pointing to the center of the retina.

Animals↗
PubMed1986

[Prognostic analysis of four pathological features in carcinoma of the uterine cervix and its clinical significance].

The correlation between different pathological features of biopsy specimen and the five year survival rate of 442 patients with carcinoma of uterine cervix treated in our hospital during 1968 to 1980, were studied by means of gradual regression. The result showed that the five year survival rate was influenced, at different levels, by the pathological features. The peritumoral lymphocytic infiltration was the most significant factor influencing the prognosis. Then were the fibrous tissue reaction and the cell type but the mode of invasion was insignificant. The best regression equation to predict the prognosis of patients with carcinoma of uterine cervix was established by gradual choosing. By this equation, we could directly calculate the probability of the five year survival of the patient. It was proved by retrospective and prospective analysis that the equation could accurately reflect the real five year survival rate of patients with carcinoma of uterine cervix.

Adult↗
PubMed1984

Inverse scattering solutions by a sinc basis, multiple source, moment method--Part III: Fast algorithms.

olving the inverse scattering problem for the Helmholtz wave equation without employing the Born or Rytov approximations is a challenging problem, but some slow iterative methods have been proposed. One such method suggested by us is based on solving systems of nonlinear algebraic equations that are derived by applying the method of moments to a sinc basis function expansion of the fields and scattering potential. In the past, we have solved these equations for a 2-D object of n by n pixels in a time proportional to n5. In the present paper, we demonstrate a new method based on FFT convolution and the concept of backprojection which solves these equations in time proportional to n3 X log(n). Several numerical examples are given for images up to 7 by 7 pixels in size. Analogous algorithms to solve the Riccati wave equation in n3 X log(n) time are also suggested, but not verified. A method is suggested for interpolating measurements from one detector geometry to a new perturbed detector geometry whose measurement points fall on a FFT accessible, rectangular grid and thereby render many detector geometrics compatible for use by our fast methods.

Humans↗
PubMedDate not supplied

Comparative molecular modeling analysis of-5-amidinoindole and benzamidine binding to thrombin and trypsin: specific H-bond formation contributes to high 5-amidinoindole potency and selectivity for thrombin and factor Xa.

The coagulation cascade enzymes thrombin and factor Xa are known to have specificity pockets very similar to those of trypsin and plasmin. However, comparative molecular modeling analysis of the crystal structures of benzamidine-thrombin and benzamidine-trypsin, in conjunction with a docking analysis of 5-amidinoindole and related inhibitors in both enzymes reveals subtle differences between the specificity sites of the two types of enzymes. Specifically, thrombin and factor Xa, which have an alanine residue at position 190, exhibit increased activities for the rigid and more bulky bicyclic derivatives of benzamidine (e.g. amidinobenzofuran, amidinothiophene and amidinoindole), because of additional hydrophobic and H-bond interactions between the inhibitors and the specificity sites, whereas enzymes with a serine residue at position 190, like trypsin and plasmin, exhibit little difference in activity among the same set of compounds because of the orientational restriction imposed on the inhibitors by Ser190, which forms an additional H-bond with the amidino group of the inhibitors. Enzymes of both groups show similar responses to the flexible aminobenzamidine since the smaller size and the rotatable anilino group of the inhibitor would allow the inhibitor to achieve favorable electrostatic interactions with both groups of enzymes. 5-amidinoindole is the most dramatic example of the rigid bicyclic type inhibitor. Based on our docking analysis, we propose that a selective H-bond with the hydroxyl group of the catalytic Ser195 and the subtle differences in steric fit imposed by Ala/Ser at position 190 explain the high potency and selectivity of 5-amidinoindole for thrombin and factor Xa.

Amino Acid Substitution↗